// SPDX-License-Identifier: GPL-2.0
/*
 * Author(s)......: Holger Smolinski <Holger.Smolinski@de.ibm.com>
 *		    Horst Hummel <Horst.Hummel@de.ibm.com>
 *		    Carsten Otte <Cotte@de.ibm.com>
 *		    Martin Schwidefsky <schwidefsky@de.ibm.com>
 * Bugreports.to..: <Linux390@de.ibm.com>
 * Copyright IBM Corp. 1999, 2001
 *
 * gendisk related functions for the dasd driver.
 *
 */

#include <linux/interrupt.h>
#include <linux/major.h>
#include <linux/fs.h>
#include <linux/blkpg.h>

#include <linux/uaccess.h>

#include "dasd_int.h"

static unsigned int queue_depth = 32;
static unsigned int nr_hw_queues = 4;
static void dasd_gd_free(struct gendisk *gdp);

module_param(queue_depth, uint, 0444);
MODULE_PARM_DESC(queue_depth, "Default queue depth for new DASD devices");

module_param(nr_hw_queues, uint, 0444);
MODULE_PARM_DESC(nr_hw_queues, "Default number of hardware queues for new DASD devices");

/*
 * Set device name.
 *   dasda - dasdz : 26 devices
 *   dasdaa - dasdzz : 676 devices, added up = 702
 *   dasdaaa - dasdzzz : 17576 devices, added up = 18278
 *   dasdaaaa - dasdzzzz : 456976 devices, added up = 475252
 */
static int dasd_name_format(char *prefix, int index, char *buf, int buflen)
{
	const int base = 'z' - 'a' + 1;
	char *begin = buf + strlen(prefix);
	char *end = buf + buflen;
	char *p;
	int unit;

	p = end - 1;
	*p = '\0';
	unit = base;
	do {
		if (p == begin)
			return -EINVAL;
		*--p = 'a' + (index % unit);
		index = (index / unit) - 1;
	} while (index >= 0);

	memmove(begin, p, end - p);
	memcpy(buf, prefix, strlen(prefix));

	return 0;
}

/*
 * Allocate and register gendisk structure for device.
 */
int dasd_gendisk_alloc(struct dasd_block *block)
{
	struct queue_limits lim = {
		/*
		 * With page sized segments, each segment can be translated into
		 * one idaw/tidaw.
		 */
		.max_segment_size = PAGE_SIZE,
		.seg_boundary_mask = PAGE_SIZE - 1,
		.max_segments = USHRT_MAX,
	};
	struct gendisk *gdp;
	struct dasd_device *base;
	unsigned int devindex;
	int rc;

	/* Make sure the minor for this device exists. */
	base = block->base;
	devindex = base->devindex;
	if (devindex >= DASD_PER_MAJOR)
		return -EBUSY;

	block->tag_set.ops = &dasd_mq_ops;
	block->tag_set.cmd_size = sizeof(struct dasd_ccw_req);
	block->tag_set.nr_hw_queues = nr_hw_queues;
	block->tag_set.queue_depth = queue_depth;
	block->tag_set.numa_node = NUMA_NO_NODE;
	rc = blk_mq_alloc_tag_set(&block->tag_set);
	if (rc)
		return rc;

	gdp = blk_mq_alloc_disk(&block->tag_set, &lim, block);
	if (IS_ERR(gdp)) {
		blk_mq_free_tag_set(&block->tag_set);
		return PTR_ERR(gdp);
	}

	/* Initialize gendisk structure. */
	gdp->major = DASD_MAJOR;
	gdp->first_minor = devindex << DASD_PARTN_BITS;
	gdp->minors = 1 << DASD_PARTN_BITS;
	gdp->fops = &dasd_device_operations;

	rc = dasd_name_format("dasd", devindex, gdp->disk_name, sizeof(gdp->disk_name));
	if (rc) {
		DBF_DEV_EVENT(DBF_ERR, block->base,
			      "setting disk name failed, rc %d", rc);
		dasd_gd_free(gdp);
		return rc;
	}

	if (base->features & DASD_FEATURE_READONLY ||
	    test_bit(DASD_FLAG_DEVICE_RO, &base->flags))
		set_disk_ro(gdp, 1);
	dasd_add_link_to_gendisk(gdp, base);
	block->gdp = gdp;
	set_capacity(block->gdp, 0);

	rc = device_add_disk(&base->cdev->dev, block->gdp, NULL);
	if (rc) {
		dasd_gendisk_free(block);
		return rc;
	}

	return 0;
}

/*
 * Free gendisk structure
 */
static void dasd_gd_free(struct gendisk *gd)
{
	del_gendisk(gd);
	gd->private_data = NULL;
	put_disk(gd);
}

/*
 * Unregister and free gendisk structure for device.
 */
void dasd_gendisk_free(struct dasd_block *block)
{
	if (block->gdp) {
		dasd_gd_free(block->gdp);
		block->gdp = NULL;
		blk_mq_free_tag_set(&block->tag_set);
	}
}

/*
 * Trigger a partition detection.
 */
int dasd_scan_partitions(struct dasd_block *block)
{
	struct file *bdev_file;
	int rc;

	bdev_file = bdev_file_open_by_dev(disk_devt(block->gdp), BLK_OPEN_READ,
				       NULL, NULL);
	if (IS_ERR(bdev_file)) {
		DBF_DEV_EVENT(DBF_ERR, block->base,
			      "scan partitions error, blkdev_get returned %ld",
			      PTR_ERR(bdev_file));
		return -ENODEV;
	}

	mutex_lock(&block->gdp->open_mutex);
	rc = bdev_disk_changed(block->gdp, false);
	mutex_unlock(&block->gdp->open_mutex);
	if (rc)
		DBF_DEV_EVENT(DBF_ERR, block->base,
				"scan partitions error, rc %d", rc);

	/*
	 * Since the matching fput() call to the
	 * bdev_file_open_by_path() in this function is not called before
	 * dasd_destroy_partitions the offline open_count limit needs to be
	 * increased from 0 to 1. This is done by setting device->bdev_file
	 * (see dasd_generic_set_offline). As long as the partition detection
	 * is running no offline should be allowed. That is why the assignment
	 * to block->bdev_file is done AFTER the BLKRRPART ioctl.
	 */
	block->bdev_file = bdev_file;
	return 0;
}

/*
 * Remove all inodes in the system for a device, delete the
 * partitions and make device unusable by setting its size to zero.
 */
void dasd_destroy_partitions(struct dasd_block *block)
{
	struct file *bdev_file;

	/*
	 * Get the bdev_file pointer from the device structure and clear
	 * device->bdev_file to lower the offline open_count limit again.
	 */
	bdev_file = block->bdev_file;
	block->bdev_file = NULL;

	mutex_lock(&file_bdev(bdev_file)->bd_disk->open_mutex);
	bdev_disk_changed(file_bdev(bdev_file)->bd_disk, true);
	mutex_unlock(&file_bdev(bdev_file)->bd_disk->open_mutex);

	/* Matching blkdev_put to the blkdev_get in dasd_scan_partitions. */
	fput(bdev_file);
}

int dasd_gendisk_init(void)
{
	int rc;

	/* Register to static dasd major 94 */
	rc = register_blkdev(DASD_MAJOR, "dasd");
	if (rc != 0) {
		pr_warn("Registering the device driver with major number %d failed\n",
			DASD_MAJOR);
		return rc;
	}
	return 0;
}

void dasd_gendisk_exit(void)
{
	unregister_blkdev(DASD_MAJOR, "dasd");
}
